Solid electrolytic capacitor and method of manufacturing the same

ABSTRACT

A conductive high polymer layer as an electrolyte is formed on the entire surface of fine pores of a dielectric oxide layer of an anode electrode having an undulated surface of fine pores or the like. As a result, a solid electrolytic capacitor having characteristics such as capacitance, impedance, and leak current exactly as designed will be obtained. It includes a manganese dioxide layer composed of a porous sinter of valve metal or roughened meal foil, placed continuously on the entire surface of the undulated surface of a dielectric oxide layer of an anode electrode having an undulated surface, a conductive high polymer layer formed by electrolytic polymerization, in contact with the surface of the manganese dioxide layer, and a cathode electrode placed on this conductive high polymer layer.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a solid electrolytic capacitor using aconductive high polymer in the electrolyte used in various electronicappliances, and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

Owing to the advancement in digital appliances, recently, capacitorshaving a low impedance and an excellent high frequency characteristiceven in a high frequency region are strongly demanded. To meet suchmarket needs, capacitors using conductive high polymers obtained bypolymerizing pyrrole, thiophene or aniline as the electrolyte are beingdeveloped and commercially produced.

Hitherto, a solid electrolytic capacitor of this kind comprises, asdisclosed in Japanese Laid-open Patent No. 63-158829, an anode electrodemade of a valve metal having a dielectric oxide layer, the dielectricoxide layer formed on this anode electrode, a conductive high polymerlayer formed by pyrolysis of manganese dioxide layer on this dielectricoxide layer, and a cathode electrode placed on this conductive highpolymer layer. The conductive high polymer layer is formed byelectrolytic process in an electrolytic polymerization solution usingmanganese dioxide layer as the anode.

Formation of conductive high polymer layer by this electrolyticpolymerization is quick in forming a conductive high polymer layer ascompared with chemical polymerization or vapor phase polymerization, andit requires a relatively simple equipment, and hence it is said to bebeneficial for industrial production.

In the prior art, however, the forming condition of manganese dioxidelayer has great effects on the principal characteristics of the solidelectrolytic capacitor such as capacitance, tan δ and impedance.

That is, when the anode electrode is formed by a method of bondingparticles of valve metal into a porous substance by sintering, or amethod of multiple etching pits by etching process, such anode electrodehas an undulated surface of an expanded surface area of fine pores orthe like. The dielectric oxide layer formed on the surface of the anodeelectrode having fine pores has multiple fine pores and exposed portionsreaching the inner depth. In the prior art, the manganese dioxide layerformed on this dielectric oxide layer is formed only on the exposedportions, and not formed in the inner parts of the fine pores. Theconductive high polymer layer is formed only on this manganese dioxidelayer. That is, in such conventional solid electrolytic capacitor, itwas possible to have a cavity in the inside. In such conventionalconstitution, when the anode electrode has an expanded undulatedsurface, sufficient capacitance and sufficient impedance correspondingto the expanded undulated surface could not be obtained. Thus, therewere serious problems also in the constitution of using conductive highpolymer as the electrolyte.

It is hence an object of the invention to present a solid electrolyticcapacitor exhibiting a desired effect sufficiently, in the solidelectrolytic capacitor using an anode electrode having an undulatedsurface and a conductive high polymer as electrolyte, and a method ofmanufacturing the same.

SUMMARY OF THE INVENTION

The solid electrolytic capacitor of the invention comprises:

(a) an anode electrode having a first undulated surface,

(b) a dielectric oxide layer placed on a first undulated surface of theanode electrode, in which the dielectric oxide layer includes a secondundulated surface placed continuously coinciding with the shape of thefirst undulated surface,

(c) a manganese dioxide layer placed on the second undulated surface ofthe dielectric oxide layer, in which the manganese dioxide layerincludes a continuous third undulated surface, placed coinciding withthe shape of the second undulated surface, on the second undulatedsurface of the dielectric oxide layer,

(d) a conductive high polymer layer placed on the third undulatedsurface of the manganese dioxide layer, in which the conductive highpolymer layer is placed on the third undulated surface of the manganesedioxide layer, and

(e) a cathode layer placed above the conductive high polymer layer.

The manufacturing method of solid electrolytic capacitor of theinvention comprises:

(a) a step of supplying an anode electrode having a first undulatedsurface,

(b) a step of forming a dielectric oxide layer on the first undulatedsurface, in which the dielectric oxide layer includes a second undulatedsurface coinciding with the first undulated surface,

(c) a step of forming a manganese dioxide layer on the second undulatedsurface, in which the manganese dioxide layer includes a continuousthird undulated surface, placed coinciding with the shape of the secondundulated surface, on the second undulated surface,

(d) a step of forming a conductive high polymer layer on the thirdundulated surface, in which the conductive high polymer layer is formedon the third undulated surface of the manganese dioxide layer, and

(e) a step of forming a cathode layer above the conductive high polymerlayer.

Preferably, the manganese dioxide layer is placed in contact with theentire surface of concave and convex portions of the second undulatedsurface.

Preferably, the conductive high polymer layer is placed in contact withthe entire surface of concave and convex portions of the third undulatedsurface.

Preferably, the first undulated surface has a surface with a pluralityof fine pores and exposed portions.

Preferably, the anode electrode having the first undulated surface has aporous sinter of valve metal or a roughened metal foil.

Preferably, the conductive high polymer layer has a conductive highpolymer layer formed by electrolytic polymerization.

Preferably, it also includes a step of impregnating the manganesedioxide layer sufficiently in a 6.5 wt. % to 26.5 wt. % aqueous solutionof manganese nitrate at 10° C. to 40° C. sufficiently, and lifting, anda subsequent step of removing the excess portion of aqueous solution ofmanganese nitrate adhered to the surface and a step of heating to morethan 80% of pyrolysis temperature within a minute and performingpyrolysis for three minutes or more at 300±10° C.

In this constitution and manufacturing method, a manganese dioxide layercan be formed on the entire surface of the undulated surface of theoxide film without damaging the dielectric oxide film of the anodeelectrode having fine pores or undulated surface. Accordingly, theconductive high polymer layer by electrolytic polymerization is formedsecurely from the inner surface of fine pores to the outer surface. As aresult, a capacitor having the capacitance, impedance, leak current andother characteristics exactly as designed is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing principal parts of a solidelectrolytic capacitor in an embodiment of the invention.

FIG. 2 is a sectional view showing principal parts of a solidelectrolytic capacitor in a comparative example of the invention.

FIG. 3 is a sectional view showing principal parts of a solidelectrolytic capacitor in other comparative example of the invention.

FIG. 4 shows the process of manufacturing method of solid electrolyticcapacitor in the embodiment of the invention.

REFERENCE NUMERALS

1 Aluminum metal foil

2 Undulated surface

2 a Fine pore

2 b Exposed portion

3 Dielectric oxide film

4 Manganese dioxide layer

5 Conductive high polymer layer

6 Cathode layer

DETAILED DESCRIPTION OF THE INVENTION

A solid electrolytic capacitor in an embodiment of the inventioncomprises

an anode electrode having a first undulated surface of porous sinter ofvalve metal or roughened metal foil,

a dielectric oxide layer having a second undulated surface placed on thefirst undulated surface of the anode electrode,

a manganese dioxide layer having a third undulated surface placed on thesecond undulated surface of the dielectric oxide layer,

a conductive high polymer layer formed by electrolytic polymerization incontact with the third undulated surface of the manganese dioxide layer,and

a cathode electrode placed on this conductive high polymer layer. Theconductive high polymer layer has a function as an electrolyte.

The first undulated surface of the anode electrode has a widened surfacehaving fine pores and exposed portions. The dielectric oxide film alsohas the second undulated surface placed on the first undulated surfacewithout gap. The manganese dioxide layer further has the third undulatedsurface placed on the second undulated surface without gap. Moreover,the conductive high polymer layer is placed on the third undulatedsurface without gap. In this constitution, the all surface regionincluding the fine pores of the expanded first undulated surface of theanode electrode acts effectively for the capacitor characteristics, and,as a result, the solid electrolytic capacitor having the characteristicsexactly as designed, such as the capacitance, impedance and leakcurrent, will be obtained.

Preferably, the manganese dioxide layer is contained by 5 to 15 ng perunit surface area 1 mm² of the dielectric layer. Herein, “ng” stands fornanogram, and 1 ng is equal to 10⁻⁹ g. If the content of the manganesedioxide layer is small than this range, the manganese dioxide layer maynot be formed in the entire surface. If the content of the manganesedioxide layer is more than this range, the manganese dioxide layer maybe formed excessively so as to plug the openings of fine pores.

Therefore, by containing the manganese dioxide layer in a range of 5 to15 ng per unit surface area 1 mm² of the dielectric layer, the capacitorhaving the characteristics exactly as designed will be realized.

Preferably, the manganese dioxide layer is formed by pyrolysis ofaqueous solution of manganese nitrate at concentration of 6.5 to 26.5wt. %. In this range of concentration, the aqueous solution of manganesenitrate permeates deeply into the fine pores, and the manganese dioxidelayer is formed on the entire surface of the dielectric oxide layer.

A manufacturing method of solid electrolytic capacitor in the embodimentof the invention includes:

a step of supplying an anode electrode having a first undulated surfaceof a porous sinter of valve metal or roughened metal foil,

a step of forming a dielectric oxide layer having a second undulatedsurface of a continuous shape coinciding with the shape of the firstundulated surface, on the first undulated surface, by forming treatmentof the anode electrode having the first undulated surface,

a step of forming a manganese dioxide layer having a third undulatedsurface of a continuous shape on the second undulated surface of thedielectric oxide layer by pyrolysis treatment, by impregnating theformed dielectric oxide layer in an aqueous solution of manganesenitrate at concentration of 6.5 to 26.5 wt. %,

a step of forming a conductive high polymer layer on the third undulatedsurface of the manganese dioxide layer by passing current in themanganese dioxide layer in an electrolytic polymerization solution, and

a step of forming a cathode electrode on the conductive high polymerlayer.

In this method, too, all the surface region including fine pores of theexpanded first undulated surface of the anode electrode acts effectivelyfor the capacitor characteristics, and, as a result, the solidelectrolytic capacitor having the characteristics exactly as designed,such as the capacitance, impedance and leak current, will be obtained.Moreover, the conductive high polymer layer corresponding to the entiresurface including the fine pores of the anode electrode can be formed.As a result, the solid electrolytic capacitor having excellentcharacteristics will be obtained.

Preferably, the aqueous solution of manganese nitrate permeates into theanode electrode in a temperature range of 10 to 40° C. In this range,the aqueous solution of manganese nitrate permeates in a short time, andbreakage of the dielectric oxide layer is prevented.

Preferably, impregnation of the aqueous solution of manganese nitratecontinues until sufficiently permeating into the fine pores of the anodeelectrode. By this method, the manganese dioxide layer is formed on theentire surface of the anode electrode.

Preferably, after impregnation of the aqueous solution of manganesenitrate into the anode electrode, the excess portion of the aqueoussolution of manganese nitrate adhered to the surface of the anodeelectrode is removed. By this method, plugging of the openings of thefine pores is prevented when forming the manganese dioxide layer.

Preferably, the pyrolysis treatment is performed at high humidity. Bythis method, a dense manganese dioxide layer is formed. As a result, thecapacitor characteristics are enhanced.

Preferably, the pyrolysis treatment is performed in a state of highhumidity with the steam content of 85±10 vol.%. By this method, a densemanganese dioxide layer is formed. As a result, the capacitorcharacteristics are enhanced.

Preferably, in the pyrolysis treatment, by heating up to 80% of thepyrolysis temperature in a minute, the pyrolysis temperature is held forat least three minutes. By this method, the dense manganese dioxidelayer is formed securely into the inner parts of the fine pores.

Preferably, the pyrolysis temperature of the pyrolysis treatment is300±10° C. By this method, a dense manganese dioxide layer is formedsecurely.

A specific embodiment of the invention is described below whilereferring to the drawings.

The constitution of the solid electrolytic capacitor in the embodimentof the invention is described while referring to FIG. 1 to FIG. 4. As anembodiment of the anode electrode, a solid electrolytic capacitor usingan aluminum metal foil roughened by etching is explained below.

FIG. 1 is a magnified sectional view of principal parts of the solidelectrolytic capacitor in the embodiment of the invention. In FIG. 1, analuminum metal foil 1 as an anode electrode includes a first undulatedsurface 2 having multiple fine pores 2 a and exposed portions 2 b formedby etching. A dielectric oxide layer 3 formed by forming treatment isplaced on the entire surface of the first undulated surface 2 of thealuminum metal foil 1. This dielectric oxide layer 3 has a secondundulated surface coinciding with the shape of the first undulatedsurface. A thin manganese dioxide layer 4 is formed on the entiresurface of the second undulated surface of the dielectric oxide layer 3(that is, the entire surface including the dielectric oxide layer 3formed in the fine pores 2 a). The manganese dioxide layer has a thirdundulated surface coinciding with the shape of the second undulatedsurface. The manganese dioxide layer has a manganese dioxide layer of acontinuous shape, formed on the second undulated surface. A conductivehigh polymer layer 5 of polypyrrole, polythiophene, or polyaniline isformed on the third undulated surface of the manganese dioxide layer 4by electrolytic polymerization method or the like. Further, a cathodeelectrode 6 of carbon paste layer or silver paste layer is placed onthis conductive high polymer layer 5.

Preferably, the manganese dioxide layer is uniformly placed on theentire surface of concave and convex portions of the second undulatedsurface, and more preferably placed in contact without gap.

The conductive high polymer layer is uniformly placed on the entiresurface of concave and convex portions of the third undulated surface,and more preferably placed in contact without gap.

The manganese dioxide layer 4 of the embodiment is formed by a weight of5 to 15 ng per unit surface area 1 mm² of the dielectric oxide layer 3.If the weight of the manganese dioxide layer 4 is less than 5 ng/1 mm²,as shown in FIG. 2, the manganese dioxide layer 4 may not be formeduniformly on the entire surface of the second undulated surface of thedielectric oxide layer 3, and, for example, the manganese dioxide layer4 may be formed in an insular shape 4 a. Accordingly, there is a portion5 a not forming the conductive high polymer layer 5, and the desiredcapacitance or impedance may not be obtained.

Or if the weight of the manganese dioxide layer 4 is more than 15 ng/1mm², as shown in FIG. 3, plugging portions 4 b may be formed in themanganese dioxide layer 4 to plug the openings of the fine pores 2. As aresult, there are gaps 5 c not forming the conductive high polymer layer5, and the desired characteristics may not be obtained.

Therefore, as the condition of forming the manganese dioxide layer 4completely also on the surface of the dielectric oxide layer 3positioned inside of the fine pores 2 a, what is important is theconcentration of aqueous solution of manganese nitrate for forming themanganese dioxide layer 4. The concentration of aqueous solution ofmanganese nitrate is preferred to be in a range of about 6.5 to about26.5 wt. %. When the concentration of aqueous solution of manganesenitrate is less than about 6.5 wt. %, the manganese dioxide layer 4cannot be formed on the surface of the dielectric oxide layer 3uniformly by a small number of times of pyrolysis treatment. When theconcentration of aqueous solution of manganese nitrate is more thanabout 26.5 wt. %, the viscosity of the aqueous solution of manganesenitrate is too high, and the aqueous solution of manganese nitratecannot permeate sufficiently into the fine pores 2. As a result, themanganese dioxide layer 4 is not formed uniformly on the surface of thedielectric oxide layer 3. That is, in order to form the manganesedioxide layer 4 uniformly on the surface of the dielectric oxide layer3, it is preferred to use the aqueous solution of manganese nitrate at aconcentration in a range of about 6.5 wt. % to 26.5 wt. %.

In the step of forming the manganese dioxide layer, it is preferred totreat the aqueous solution of manganese nitrate adhered to the surfaceof the dielectric oxide Layer by pyrolysis in an atmosphere of highhumidity, or an atmosphere containing 85±10 vol. % of steam. If havingthe manganese dioxide layer formed at humidity out of this humidityrange, the characteristics of the solid electrolytic capacitor areslightly inferior.

Typical embodiments are described below, but it must be noted that theinvention is not limited to these embodiments alone.

Embodiment 1

The process of manufacturing method of the solid electrolytic capacitorin the embodiment of the invention is shown in FIG. 4. A roughenedaluminum metal foil is prepared. The aluminum metal foil has anundulated surface 2 having multiple fine pores 2 a and exposed portions2 b formed by etching process so that the surface area may be about 125times. That is, the aluminum metal foil has a roughened surface. In partof the surface of the aluminum metal foil, an electric insulating resisttape was glued, and the cathode electrode and anode electrode wereseparated. Thus, an anode electrode 1 having an effective area of 3.2mm×3.9 mm was fabricated. This anode electrode 1 was immersed in anaqueous solution of ammonium dihydrogenphosphate at concentration of 0.3wt. % at liquid temperature of 70° C., and a direct-current voltage of12 V was applied for 20 minutes. Thus, a dielectric oxide layer 3 wasformed on the surface of the aluminum metal foil.

In succession, the anode electrode 1 having the dielectric oxide layer 3was immersed in an aqueous solution of manganese nitrate atconcentration of 20 wt. % at liquid temperature of 25° C. for 3 seconds,and was lifted from the aqueous solution. Then, the excess portion ofthe aqueous solution of manganese nitrate adhered to the surface of thedielectric oxide layer 3 of the anode electrode 1 was removed by blowingout with air. Then, within one minute after lifting the anode electrode1 adhered with the aqueous solution of manganese nitrate on the surfaceof the dielectric oxide layer 3 from the aqueous solution, it was heatedto over 250° C., and treated by pyrolysis at 300° C. for five minutes.Thus, the manganese dioxide layer 4 was formed on the surface of thedielectric oxide layer 3 of the anode electrode 1. The pyrolysis wastreated in the atmosphere containing about 85±10 vol. % of steam.

Then, the anode electrode 1 having the manganese dioxide layer 4 wasimmersed in an aqueous solution of ammonium dihydrogenphosphate atconcentration of 0.3 wt. % at liquid temperature of 70° C., and adirect-current voltage of 10 V was applied for 10 minutes. Thus, theanode electrode having the manganese dioxide layer 4 was re-formed. Onthe manganese dioxide layer, a conductive high polymer layer 5 made ofpolypyrrole film was formed by electrolytic polymerization method. Onthe conductive high polymer layer 5, further, carbon paste and silverpaste were applied sequentially, and a cathode electrode 6 was formed.Terminals were placed in the device having thus formed anode electrode1, dielectric oxide layer 3, manganese dioxide layer 4, and conductivehigh polymer layer 5. By resin molding of the outer surface of thedevice, the casing was formed. Thus, the solid electrolytic capacitorwas manufactured.

Embodiment 2

In the foregoing embodiment 1, an aqueous solution of manganese nitratehaving a concentration of 25 wt. % was used. A solid electrolyticcapacitor was prepared in the same manner as in embodiment 1 except forthis method.

Embodiment 3

In the foregoing embodiment 1, an aqueous solution of manganese nitratehaving a concentration of 35 wt. % was used. A solid electrolyticcapacitor was prepared in the same manner as in embodiment 1 except forthis method.

Embodiment 4

The temperature of the aqueous solution of manganese nitrate is 50° C. Asolid electrolytic capacitor was prepared in the same manner as inembodiment 1 except for this method.

Embodiment 5

In the foregoing embodiment 1, the time of immersing the anode electrodein the aqueous solution of manganese nitrate was 0.5 sec. A solidelectrolytic capacitor was prepared in the same manner as in embodiment1 except for this method.

Embodiment 6

In the foregoing embodiment 1, the excess aqueous solution of manganesenitrate was pyrolyzed without blowing away. A solid electrolyticcapacitor was prepared in the same manner as in embodiment 1 except forthis method.

Embodiment 7

In the foregoing embodiment 1, the pyrolysis was performed withoutapplying humidity in the process of pyrolysis. A solid electrolyticcapacitor was prepared in the same manner as in embodiment 1 except forthis method.

Embodiment 8

In the foregoing embodiment 1, the humidity in pyrolysis process wasadjusted to 50% RH. A solid electrolytic capacitor was prepared in thesame manner as in embodiment 1 except for this method.

Embodiment 9

In the foregoing embodiment 1, the time required for heating up to 250°C. was more than three minutes after lifting the anode electrode fromthe aqueous solution, and the holding time at 300° C. was one minute. Asolid electrolytic capacitor was prepared in the same manner as inembodiment 1 except for this method.

Embodiment 10

In the foregoing embodiment 1, the pyrolysis temperature was 250° C. Asolid electrolytic capacitor was prepared in the same manner as inembodiment 1 except for this method.

Using various solid electrolytic capacitors fabricated in these manners,initial characteristics were measured. Results are summarized inTable 1. The measuring temperature was 25 to 30° C. The capacitance andtan δ was measured at 120 Hz, and the impedance was measured at 400 kHz.To measure the leak current, after applying direct-current voltage of6.3 V, the current was measured 30 seconds later. In each one of thesesamples of the embodiments, 30 capacitors were used, and the average of30 pieces is shown in Table 1. In the samples of embodiments 1 to 3, thesolid electrolytic capacitors were completely dissolved, and the depositamount of manganese dioxide was measured by atomic absorption method.

TABLE 1 Deposit amount of Leak maganese Capacitance tan δ Impedancecurrent dioxide (μF) (%) (mΩ) (nA) (ng/mm²) Embodiment 1 10.35 0.9 48 2511.7 Embodiment 2 11.05 0.8 45 28 14.1 Embodiment 3 8.63 1.7 102  3021.5 Embodiment 4 10.42 0.9 53 236  — Embodiment 5 7.54 2.3 113  60 —Embodiment 6 9.20 1.8 107  32 — Embodiment 7 9.21 1.2 80 354  —Embodiment 8 9.59 1.1 74 267  — Embodiment 9 8.59 1.1 95 53 — Embodiment10 8.27 0.8 88 42 —

As clear from Table 1, in the solid electrolytic capacitors manufacturedby the manufacturing methods of embodiments 1 and 2, without damagingthe dielectric oxide layer of the anode electrode having fine pores, themanganese dioxide layer was formed uniformly on the entire surface offthe second undulated surface including the fine pores and exposedportions of the dielectric oxide layer. Accordingly, the conductive highpolymer layer in the subsequent step of electrolytic polymerization wassecurely formed on the entire surface of the inner surfaces of finepores and exposed portion surfaces of the third undulated surface. Allcharacteristics of capacitance, tan δ impedance and leak currentsatisfied the desired values. By contrast, as shown in embodiments 3 to10, the capacitors manufactured in the methods of high concentrationcondition of aqueous solution of manganese nitrate, high temperaturecondition, short immersion time condition, condition without removal ofexcessive adhered portion, insufficient condition of humidity inpyrolysis process, long heating time condition to pyrolysis temperature,or low pyrolysis temperature condition were inferior in some of thecharacteristics of capacitance, tan δ, impedance and leak current ascompared with the capacitors manufactured in the conditions ofembodiments 1 and 2.

Thus, according to the method of the invention, without damaging thedielectric oxide layer of the anode electrode having the undulatedsurface of fine pores and the like, a manganese dioxide layer continuousto the undulated surface can be formed on the entire surface ofundulated surface including the inner surface of fine pores and exposedportion surfaces. Gaps in the undulated surface are decreasedsignificantly. Accordingly, the conductive high polymer layer byelectrolytic polymerization can be formed securely on the entire surfacefrom the inner surfaces of fine pores to the outer surfaces. Therefore,the solid electrolytic capacitor having excellent characteristics in allcharacteristics including capacitance, impedance and leak current can beobtained.

What is claimed is:
 1. A solid electrolytic capacitor comprising: (a) ananode electrode having a first undulated surface, (b) a dielectric oxidelayer placed on said first undulated surface of said anode electrode,said dielectric oxide layer having a second undulated surface placedcontinuously coinciding with the shape of said first undulated surface,(c) a manganese dioxide layer placed on said second undulated surface ofsaid dielectric oxide layer, said manganese dioxide layer having a thirdundulated surface placed continuously coinciding with the shape of saidsecond undulated surface, on said second undulated surface of saiddielectric oxide layer, (d) a conductive high polymer layer placed onsaid third undulated surface of said manganese dioxide layer, and acathode layer placed above said conductive high polymer layer.
 2. Thesolid electrolytic capacitor of claim 1, wherein said first undulatedsurface has a surface with a plurality of fine pores and exposedportions.
 3. The solid electrolytic capacitor of claim 1, wherein saidanode electrode having said first undulated surface has a porous sinterof valve metal.
 4. The solid electrolytic capacitor of claim 1, whereinsaid anode electrode having said first undulated surface has a roughenedmetal foil.
 5. The solid electrolytic capacitor of claim 1, wherein saidconductive high polymer layer has a conductive high polymer layer formedby electrolytic polymerization.
 6. The solid electrolytic capacitor ofclaim 1, wherein said first undulated surface has first fine pores andfirst exposed portions, said second undulated surface has second finepores and second exposed portions, and said manganese dioxide layer isplaced on an entire surface of a surface of said second fine pores ofsaid dielectric oxide layer and a surface of said second exposedportions thereof.
 7. The solid electrolytic capacitor of claim 1,wherein said anode electrode having said first undulated surface has atleast one of porous sinter of valve metal and roughened metal foil, saidconductive high polymer layer has a conductive high polymer layer formedby electrolytic polymerization, and said manganese dioxide layer isplaced on the entire surface of said dielectric oxide layer.
 8. Thesolid electrolytic capacitor of claim 1, wherein said manganese dioxidelayer is placed in a range of about 5 ng to about 15 ng in 1 mm² of saiddielectric oxide layer.
 9. The solid electrolytic capacitor of claim 1,wherein said manganese dioxide layer is a layer formed by pyrolysis ofaqueous solution of manganese sulfate in a concentration range of about6.5 wt. % to 26.5 wt. %.
 10. The solid electrolytic capacitor of claim1, wherein said manganese dioxide layer is placed in contact with anentire surface of a concave and a convex portion of said secondundulated surface.
 11. The solid electrolytic capacitor of claim 1,wherein said conductive high polymer layer is placed in contact with anentire surface of a concave and a convex portion of said secondundulated surface.